Thousands of Hong Kong-owned factories in southern China's booming manufacturing region face closure or relocation due to the pollution and environmental hazards they pose.

A haze of pollution is seen over the Hong Kong skyline. Thousands of Hong Kong-owned factories in southern China's Pearl River Delta face closure or relocation due to the pollution and environmental hazards they pose. [AFP]

The moves are part of efforts by China's Guangdong province to force polluting, high-risk and energy-inefficient factories out of the Pearl River Delta.

It is also aimed at promoting sustainable development and cleaner production, according to the South China Morning Post.

Peter Leung Pak-yan, director of Hong Kong's Guangdong Economic and Trade Office, said businesses should act quickly to come up with survival plans.

"My personal observation is that the situation is getting more serious and time is running out quickly," he was quoted as saying.

The newspaper said about 300 dangerous goods manufacturers were notified earlier this year that their licences would not be renewed by the end of June, or would only be renewed on a monthly basis, until they agreed to move to designated industrial areas.

Industries directly affected include electroplating, dyeing, chemicals, paints, detergents and production of dangerous substances.

Beijing-backed newspaper Ta Kung Pao estimated that 50,000 companies will be affected.

A spokeswoman for the 3,000-member Federation of Hong Kong Industries said their members have expressed concern about the policy and the group is following it up on the mainland.

Serious pollution blights large parts of China as a consequence of its rapid economic development.

In 2004 nearly 2.5 million tons of pollutants produced by agriculture and industry flowed into the mouth of the Pearl River, according to the Guangzhou Marine Geological Survey.

It has said the contamination includes heavy metals, oil, nitrogen, ammonia and other chemical materials with levels of pollutants far higher than standards set by the State Environmental Protection Administration.